今年美国签证形势整体开始发生转变，敏感专业的审查周期从以前的长达两个月缩短到2~3周，且因专业审查而遭遇申请失败的人数极少。但是，如果申请者所学的专业属于敏感专业，为了能按时到达学校，一定要提早向所在辖区的大使馆或者领事馆申请签证。

　　美国留学 敏感专业详细列表

　　The State Department maintains a Technical Alert List, also known as the sensitive major list, to guide their evaluation of visa submission.

　　Sorted by rate.

　　CRITICAL FIELDS LIST

　　A. CONVENTIONAL MUNITIONS: Technologies associated with:

　　-- Warheads and other large caliber projectiles

　　-- Reactive armor and warhead defeat systems

　　-- Fusing and arming systems.

　　-- Electronic countermeasures and systems

　　-- New or novel explosives and formulations

　　-- Automated explosive detection methods and equipment

　　B. NUCLEAR TECHNOLOGY: Technologies associated with

　　production and use of nuclear material for both peaceful and military applications. Included are technologies for:

　　-- Enrichment of fissile material

　　-- Reprocessing irradiated nuclear fuel to recover produced

　　plutonium

　　-- Production of heavy water for moderator material

　　-- Plutonium and tritium handling

　　Also, certain associated technologies related to nuclear physics and/or nuclear engineering. Includes materials,equipment or technology associated with:

　　-- Power reactors, breeder and production reactors

　　-- Fissile or special nuclear materials

　　-- Uranium enrichment, including gaseous diffusion,centrifuge, aerodynamic, chemical, Electromagnetic Isotopic Separation (EMIS), Laser Isotope Separation

　　(LIS)

　　-- Spent fuel reprocessing, plutonium, mixed oxide nuclear research

　　Inertial Confinement Fusion (ICF)

　　-- Magnetic confinement fusion

　　-- Laser fusion, high power lasers, plasma,

　　-- Nuclear fuel fabrication including Mixed Oxide (uranium-

　　plutonium) fuels (MOX)

　　-- Heavy water production

　　-- Tritium production and use

　　-- Hardening technology

　　C. ROCKET SYSTEMS (including ballistic missile systems,space launch vehicles and sounding rockets) and Unmanned Air Vehicles (UAV) (including cruise missiles, target drones, and reconnaissance drones): Technologies associated with rocket systems and UAV systems. The technology needed to develop a satellite launch vehicle is virtually identical to that needed to build a ballistic missile.

　　D. ROCKET SYSTEM AND UNMANNED AIR VEHICLE (UAV) SUBSYSTEMS:

　　Propulsion technologies include solid rocket motor stages,and liquid propellant engines. Other critical subsystems include re-entry vehicles, guidance sets, thrust vector controls and warhead safing, arming and fusing. Many of these technologies are dual-use. Technologies include:

　　-- Liquid and solid rocket propulsion systems

　　-- Missile propulsion and systems integration

　　-- Individual rocket stages or staging/separation mechanism

　　-- Aerospace thermal (such as superalloys) and high-performance structures

　　-- Propulsion systems test facilities

　　E. NAVIGATION, AVIONICS AND FLIGHT CONTROL USEABLE IN ROCKET SYSTEMS AND UNMANNED AIR VEHICLES (UAV): These capabilities directly determine the delivery accuracy and lethality of both unguided and guided weapons. The long-term costs to design, build and apply these technologies have been a limiting proliferation factor. Technologies include those associated with:

　　-- Internal navigation systems

　　-- Tracking and terminal homing devices

　　-- Accelerometers and gyroscopes

　　-- Rocket and UAV and flight control systems.

　　-- Global Positioning System (GPS)

　　F. CHEMICAL, BIOTECHNOLOGY AND BIOMEDICAL ENGINEERING: The technology used to produce chemical and biological weapons is inherently dual-use. The same technologies that could be applied to develop and produce chemical and biological weapons are used widely by civilian research laboratories and industry; these technologies are relatively common in many countries. Advanced biotechnology has the potential to support biological weapons research. In the biological area, look for interest in technologies associated with:

　　-- Aerobiology (study of microorganisms found in the air or in aerosol form)

　　-- Biochemistry

　　-- Pharmacology

　　-- Immunology

　　-- Virology

　　-- Bacteriology

　　-- Mycology

　　-- Microbiology

　　-- Growth and culturing of microorganisms

　　-- Pathology (study of diseases)

　　-- Toxicology

　　-- Study of toxins

　　-- Virulence factors

　　-- Genetic engineering, recombinant DNA technology

　　-- Identification of nucleic acid sequences associated with pathogenecity

　　-- Freeze-drying (lyophilization)

　　-- Fermentation technology

　　-- Cross-filtration equipment

　　-- High "DOP-rated filters" (e.g., HEPA filters, ULPA filters)

　　-- Microencapsulation

　　-- Aerosol sprayers and technology, aerosol and aerosolization technology

　　-- Spray or drum drying technology

　　-- Milling equipment or technology intended for the production of micron-sized particles

　　-- Technology for eliminating electrostatic charges of small particles

　　-- Flight training

　　-- Crop-dusting, aerosol dissemination

　　-- Unmanned aerial vehicle (UAV) technology

　　-- Fuses, detonators, and other munitions technology

　　-- Submunitions technology

　　-- Computer modeling of dissemination or contagion

　　-- Chemical absorption (nuclear-biological-chemical (NBC)protection)

　　In the chemical area, look for:

　　-- Organo-phosphate chemistry

　　-- Neurochemistry

　　-- Chemical engineering

　　-- Chemical separation technology

　　-- Pesticide production technology

　　-- Pharmaceutical production technology

　　-- Chemical separation technology

　　-- Toxicology

　　-- Pharmacology

　　-- Neurology

　　-- Immunology

　　-- Detection of toxic chemical aerosols

　　-- Chemical absorption (Nuclear-Biological-Chemical (NBC)protection)

　　-- Production of glass-lined steel reactors/vessels, pipes,flanges, and other equipment

　　-- Aerosol sprayers and technology

　　-- Flight training

　　-- Crop-dusting, aerosol dissemination

　　-- Unmanned Aerial Vehicle (UAV) technology

　　-- Fuses, detonators, and other munitions technology

　　-- Submunitions technology

　　-- Computer modeling of dissemination

　　G. REMOTE SENSING, IMAGING AND RECONNAISSANCE: Satellite and aircraft remote sensing technologies are inherently dual-use; increasingly sophisticated technologies can be used for civilian imagery projects or for military and intelligence reconnaissance activities. Drones and remotely piloted vehicles also augment satellite capabilities. Key-word associated technologies are:

　　-- Remote sensing satellites

　　-- High resolution multi-spectral, electro-optical and radar data/imagery

　　-- Imagery instruments, cameras, optics, and synthetic aperture radar systems

　　-- Ground receiving stations and data/image processing systems

　　-- Photogrammetry

　　-- Imagery data and information products

　　-- Piloted aircraft

　　-- Unmanned Air Vehicles (UAV)

　　-- Remotely-piloted vehicles; and drones

　　H. ADVANCED COMPUTER/MICROELECTRONIC TECHNOLOGY: Advanced computers and software play a useful (but not necessarily critical) role in the development and deployment of missiles and missile systems, and in the development and production of nuclear weapons. Advanced computer capabilities are also used in over-the-horizon targeting,airborne early warning targeting, Electronic Countermeasures (ECM) processors. These technologies are associated with:

　　-- Supercomputing, hybrid computing

　　-- Speech processing/recognition systems

　　-- Neural networks

　　-- Data fusion

　　-- Quantum wells, resonant tunneling